The present invention concerns a device for positioning masking strips in a metallizing machine, notably a machine for metallizing wide dielectric film giving a film with metallized zones and non-metallized zones.
At present, to manufacture capacitors with metallized dielectric film of stacked or rolled type, plastic films are used which have a metallized zone and a lateral non-metallized margin. These metallized flexible plastic films with a non-metallized margin are obtained using a process in two stages. During the first stage, a wide flexible dielectric film such as a polyester, polycarbonate. polysulfone, polypropylene or similar film is metallized by a process of evaporation under vacuum in a metallizing machine. The metallization is performed by evaporating a metal such as aluminium, zinc, alloys containing aluminium, zinc, chrome or similar. The non-metallized margins are obtained during the process of evaporation under vacuum, by using a set of masking strips enabling non-metallized parts to be obtained on the wide film. In metallizing machines used at present, the device for positioning the masking strips is constituted of several grooved rollers which drive the masking strips. This device has a number of disadvantages. It requires a set of at least two rollers, more often three or four, with grooves of the same width. In addition, it is necessary to have a set of rollers for each width of masking strip. Moreover the positioning of the rollers inside the metallizing machine is often a long and complex task since it is necessary to remove and replace several rollers each time a film with non-metallized zones of different width is required.